Squizzumables

V1.53

- Guild invite: now hidden for players who are already in any guild (invite would just fail)
  - Unit-based menus (party, raid, target, focus): checks GetGuildInfo(unit) to detect any guild membership
  - Name-based menus (friend list, chat roster, etc.): checks if player is in our specific guild via roster scan
- Guild invite: rewritten to use the modern WoW 12.0 Menu.ModifyMenu API
  - Covers all popup types: Party, Raid, Player, Friend, Guild, Chat Roster, Target, Focus, Arena Enemy, and more
  - Fixed permission check to use the correct global CanGuildInvite() API
  - Fixed invite call to use C_GuildInfo.Invite() (correct C_GuildInfo namespace)
  - Cross-realm support: correctly appends -Server for players on different realms